#pragma once

/*
* Blake2b pseudo random number generator: https://github.com/tevador/RandomX/blob/master/doc/specs.md#35-blakegenerator
* This is used for RandomX superscalar program generation.
*/

#include "blake2b.hpp"

namespace modernRX::blake2b {
    // Holds generator's current state (which is 64-bytes blake2b hash) and allows to get 8- or 32-bit values.
    class alignas(64) Random {
    public:
        // Calculates blake2b hash from given seed and nonce and set it as a current state.
        // Seed max size is 60 bytes (bigger buffers will be truncated).
        [[nodiscard]] explicit Random(const_span<std::byte> seed, const uint32_t nonce = 0) noexcept;

        // Return 8-bit unsigned int. Rehashes state if no bytes available. 
        [[nodiscard]] uint8_t getUint8() noexcept;

        // Return 32-bit unsigned int. Rehashes state if less than 4 bytes available.
        [[nodiscard]] uint32_t getUint32() noexcept;
    private:
        // Generates new state (blake2b hash) if left less bytes than needed.
        void rehashIfNeeded(const size_t bytes_needed) noexcept;

        std::array<std::byte, Max_Digest_Size> state{};
        uint32_t position{ 0 };
    };
}